I'd like to mention beforehand that this is my first time writing and would appreciate any feedback on what I'm doing wrong, thanks.

The SCP is a classic WW2 radio set that, when told what it deems to be a secret, will respond with a secret of its own. it would start by telling you something completely random, but as you tell it more secrets it adapts to your personality and learns about you and will make active attempts to harm you mentally by telling you things like when you will die, that your spouse has cheated on you, the truth about the universe. I'd like to have it mention SCP-2521, or have an incident where there was a containment breach and it helped a D-class break it out but I don't really have a clue how to go about doing that.

obviously, it would be more story-driven so test logs and incident logs would be taking a decent portion of the entry.

with a bit of creativity, I believe that it could be an interesting read.

Well, yes. So what are you going to do with it? What creative things do you have planned for this item?

I might not be getting exactly what you are trying to write here. If I understand correctly, what you want is a radio that can hear people's secrets, and will tell a secret in return. And that's probably fine, but it's only fine. There's nothing here that particularly sticks out to me as interesting.

Things that do things are only as interesting as the stories that surround them. So what's the story here? What are the circumstances of its discovery? What was it used for before the Foundation got to it? What does the Foundation do with it? How does it affect the world around it?

I suggest taking the time to read a few guides. Here's my recommendations:

I had planned beforehand of it being found in an army base during world war two and being picked up because of the suicides caused by it. obviously, since its an army radio during the war, more or less all of the things being spoken through it would've been recognized as secrets and thus the radio would respond with its own, most likely being that the operator's wife had cheated on him whilst he was away or something. I've been having trouble finding a way to figure out how the foundation would find how to use it though, as 'telling it a secret' isn't exactly something obvious.

I had a few ideas about what the foundation would do with it, eg. testing it on people with little outside connection, people with high intellect, people who don't feel emotion.

I think an interesting plot point might be that if someone talks to the device more than once, the secrets released become more damaging each time. It could start with petty nonsense, then build up to horrifying truths. Also, if the device began spouting off about Foundation secrets such as SCPs, and these leaks become worse and worse, how would the foundation react?

I think that would be interesting. Depending on how resilient the device is meant to be, it could survive the attack, that's up to you, but I personally would like to see the thing stick around instead of being destroyed. Also, maybe the device could be used to figure out where SCP-2521 takes things that mention it. Anything that would keep the device from becoming lost is what I would prefer.

Like what if during a test with D-Class personnel it mentions the names of all of the O5 personnel? I imagine that if the device couldn't be destroyed, the foundation would at least want to keep it under lock and key to avoid data leaks.

The device could also be used to investigate information about unknown SCPs. Although most information from it should be damaging secrets, it might throw in a few pieces of good information here and there just to keep people talking.

Also, would you want the radio to be somewhat self aware with the secrets it tells? Maybe telling secrets that somehow serve its own interests or amusement? Like what if during a test with a D class that wanted to escape it could tell secrets like: "confinement procedures on such and such SCP are down, when you hear a tremor, make an escape in the madness," "you can't escape without my help; bring me along," or "there is a guard when you round this corner, go the other way."

Not feeling this idea. The anomaly feels somewhat simplistic and it doesn't lend itself easily to the modern SCP format. Even if the radio gave out a true secret, how would anyone verify it? It's not a hard fact. It could just be lying. Nobody's going to take what a radio says as fact.

If this radio talks about SCP-2521 it'd just… take the radio. That's the entire anomaly. It's a nitpick I know but it should be said.

The idea that the anomaly should "make active attempts to harm you mentally […]" just doesn't do anything for me. Things don't have to be dangerous to be interesting, nor do they need side-effects to balance out their benefits. It would make sense for the radio (and/or the person behind it) to have its own desires and motives, but having that be "hurting people" doesn't make much sense to me.

I do somewhat like the idea of a secret-hungry radio that gives you something in return as a core anomaly, but the rest of it doesn't do anything for me. No greenlight.